1. Field of the Invention
The present invention relates to a method of patterning a transparent electrode of Indium Tin Oxide (ITO) and, more particularly, to a method of crystallizing the transparent electrode of ITO.
2. Description of the Related Art
A transparent conductive layer of Indium Tin Oxide (ITO) is practically applied to the fabrication of a contact of contact panel, an electrode of liquid crystal display (LCD), a thermal reflective coating, a gas-sensing sensor, a static electricity-resistance coating, and an abrasion-resistance coating of glass. The ITO layer may be formed by a chemical film-forming method, such as spray, chemical evaporation, or dipping. Alternatively, the ITO layer may be formed by a physical film-forming method, such as vacuum evaporation or sputtering. Generally, sputtering can form an ITO layer of a low resistance and a uniform thickness on a substrate. However, when the ITO layer is then patterned by conventional photolithography and etching with oxalic acid, the patterned ITO layer cannot fit in with the requirements for product properties.
FIG. 1 is a flow chart of a conventional method of patterning an ITO layer. First, at step 10 of sputtering, an amorphous ITO layer is deposited on a substrate. Then, conventional photolithography, which comprises a step 12 of photoresist coating, a step 14 of soft baking, a step 16 of exposure, a step 18 of developing, a step 20 of hard baking, a step 22 of etching by oxalic acid, and a step 22 of photoresist stripping, is carried out on the amorphous ITO layer. The step 14 of soft baking drives out the solvents existing in the photoresist. The step 16 of exposure makes the photoresist absorb appropriate energy so as to proceed with photochemical transformation. The step 18 of developing forms the potential pattern that is transferred to the photoresist. The step 20 of hard baking is used to further reduce the solvent remaining in the photoresist and fix the profile of the patterned photoresist. The step 22 of etching by oxalic acid removes the amorphous ITO layer not covered by the patterned photoresist, thus forming the pattern of the amorphous ITO layer. Finally, at step 26, annealing is performed in an oven to turn the amorphous ITO layer into a crystallized ITO layer. Thus the ITO layer can achieve the expected resistance and transparency.
However, at the step 10 of sputtering with H2O, when the amorphous ITO layer is continuously deposited to reach a thickness of more than 800 xc3x85, the process temperature is lower than the process temperature in the subsequent step 20 of hard baking. Thus, the higher temperature in the step 20 of hard baking causes a microcrystalline phenomenon on the surface of the amorphous ITO layer. Also, when the process temperature is improperly controlled in sputtering or photolithography, the microcrystalline phenomenon can be formed. Since oxalic acid is not the excellent etchant for etching crystallized materials, the step 22 of etching cannot completely remove the crystalline area of the ITO layer and this decreases the accuracy of patterning the ITO layer.
In addition, in the series of steps 12xcx9c24,exposured photoresist and developer solution are easily remained on the substrate, thus effecting the properties of the subsequent etching or deposition. Also, the complicated steps 12xcx9c26 have high production costs and may cause the substrate to be bended, damaged or contaminated if man-made carelessness and improper process control occur.
Thus, a method of patterning an ITO layer solving the aforementioned problems is called for (desired).
The present invention provides a method of patterning an ITO layer to pattern and crystallize the amorphous ITO layer at the same time so as to simplify the procedure.
The method of patterning an indium tin oxide (ITO) layer is performed on a glass substrate. First, using sputtering, an amorphous ITO layer is deposited on the glass substrate. Then, using excimer laser annealing (ELA), the amorphous ITO layer within a predetermined pattern is turned into a crystalline ITO layer. Finally, using an etch solution, the amorphous ITO layer outside the predetermine pattern is removed.
Accordingly, it is a principle object of the invention to provide excimer laser annealing for replacing the conventional photolithography process.
It is another object of the invention to use excimer laser annealing to pattern and crystallize the amorphous ITO layer at the same time.
Yet another object of the invention is to simply the method of patterning the ITO layer.
It is a further object of the invention to accurately pattern the ITO layer.